Moisture indication and control



Dec. 31, 1929.

G. s. WITHAM, JR 1,741,266

MOISTURE INDICATION AND CONTROL Filed April 30, 1926 INVENTOR *fW %21; TI NEY Patented Dec. 31, 1929 PATENT OFFICE GEORGE S. WITHAM, JR., 0]? HUDSON FALLS, NEW YORK MOISTURE INDICATION AN D CONTROL Application filed April 30, 1926. Serial No. 105,680.

This invention relates to methods and apparatus for indicatingor determining and controlling the moisture condition of an element, and is particularly applicable tothe indication or control of the moisture content of a traveling web of any suitable material. For example, in paper mills it is particularly desirable to indicate or control the moisture of a traveling web of paper under process of manufacture. In the manufacture of paper Webs it has been common practice to determine the moisture content by feeling of sections thereof, and regulating the drying agent in accordance with the impression of the operator or attendant who feels the paper. Obviously such a method is very uncertain, both because of the possibility of error in the judgment of the attendant, and the fact that a very noticeable change in the moisture content of the web may occur between the intervals at which the paper web is felt of by the attendant.

Thepresent invention is in the nature of an improvement upon the invention disclosed in my prior application, now Patent Re. 17,049, and it has for an ob ect the improvement of the methods and apparatus of indicating or controlling the moisture content;

of any object, and obtaining the indication or control in a-more definite and scientific manner, and as-largely as possible independently of the judgment of the attendants. A further object is to provide such methods and apparatus with which the drying agent Wlll be controlled effectively and efiiciently, and also in a safe manner in case a traveling web whose moisture condition is to be controlled,

should break.

a simple box associated therewith, both form ing a part of the invention;

Fig. 3 is a sectional elevation of one of the sample boxes showing the relation of the sample ox to a web;

Fig. 4 is a diagrammatic View of other details employed in connection with the apparatus shown in Fig. 1; and

' Fig. 5 is an enlarged sectional plan of a portion of one of the connections to the sample box. v

In order that the nature of the invention may be understood, the invention will be explained as it may be applied to the control of a paper web in a paper mill, the apparatus for the same being shown in the accompanying drawing. The paper web A m approaching the present apparatus passes over a roller 4 and thence successively over and around the series of drier rolls 5. After leaving the last roll 5 of the series the web is conducted around the roller 6 and thence to a series of other rolls 7 An endless web 8 of suitable material having an aflinity or attraction for moisture, such as felt, serves as a drier belt and is conducted over the roller 4 where it meets the web A, and then with the paper web over and around the successive drier rolls 5. The web 8 may leave the last roll 5 of the series just prior to the point where the web A leaves the same roll. The drier felt 8, after leaving the last roll 5 of the series, is conducted around rollers 9, 10, and 10 back to the roller 4.

In this construction, as usual, the drier rolls 5 are heated by steam or other medium, and the quantity of steam or heat admitted is regulated in accordance with the moisture content of the paper web. Inasmuch as the drier felt will travel in intimate contact with the paper web for a considerable dis tance and while subjected to heat, it will absorb a considerable amount of moisture from the paper web and when separated from the web at the point where leaving the last roll 5, its moisture condition will be a reliable indication of the moisture condition of theweb leaving the drier rolls. I, therefore, propose thus somewhat indirectly to determine the moisture content of the paper web by determining or indicating the moisture content of the drier felt.

For this purpose a box 11, which may be referred to hereinafter as a sample box, is disposed adjacent the drier felt, preferably at a point soon after it has been separated from the paper web, such as between the rollers 9 and 10. The sample box 11 may be of elongated form, having an open side which.

faces and is substantially closed by a face of the traveling drier felt 8. The sample box, therefore, serves to confine over a limited area of a face of the drier felt, a small quantity of a suitable gas, such as air which will take up moisture from the drier felt. A pipe 12 connects one end of the interior of the sample box with the intake side of a blower or fan 13, the latter having its outlet connected by a pipe 14 to a psychrometer or hygrometric instrument 15, which may contain the usual wet and dry bulb thermometers for indicating the humidity of the gas or air which passes thereover. The operation of such hygrometric instruments is well understood and requires no specific explanation.

This instrument is preferably of a type having an indicating dial 16, which indicates either directly or indirectly the moisture content or humidity of the gas passing over the wet and dry bulb thermometers in the instrument. From this it will be observed that the air drawn through the sample box and in contact with the drier felt will take up moisture from the felt, andthis air will be forced by the blower or fan 13 over and around the wet and dry bulb ther mometers so as to cause an indication on the dial 15 of the humidity of such air or gas. This indication on the dial 15 will then be a function of the moisture content of the drier felt, and therefore, of. the paper web. The dial 15 may, if desired, be calibrated to read directly in percentage of moisture in the paper web.

The dial actuating mechanism is preferably enclosed in a dial box 17, and may be of the type adapted to control a supply of compressed air or gas in accordance with the variations of.the humidity indication. Inasmuch as such instruments are well known in the art and .commerically available, they have been illustrated conventionally, and an explanation of their specific mechanism appears to be unnecessary in the present case.

' With such instruments a pipe 18 connects the dial box 17 with a suitable source (not shown) of compressed gas or air, and the dial box contains suitable mechanism for controlling the passage of this compressed air from the pipe 18 to one or more other pipes 19 leading to controlling mechanism 20 for the steam or other heating medium, also common in the art and for that reason shown only conventionally.

Thus steam from a suitable supply pipe 21 20, which is in turn responsive to the moisture content of the drier felt. As the moisture content of the drier felt is a function of the moisture content of the paper web which has just left the machine, the moisture content of the webwill thus be automatically controlled by the moisture content of the drier felt.

While it is desirable to obtain an indication of the moisture content of a traveling paper web in the manner hereinbefore described, it is also desirable in some instances to be able to secure, such-as for the purpose of comparison, a direct indication of the moisture content of the web. Accordingly I may also mount another sample box 23, similar to the sample box 11, in proximity to and closed by the web A, just after it leaves the last roll of the series of drier rolls 5, and after its separation from the drier felt. The interior of one end of this sample box 23 may be connected by a pipe 24 to the pipe 12 which connects the sample box 11 to the fan or blower 13. This connection to the pipe 12 may conveniently be made by a branch or Y-pipe connector 25, so that the air supplied to the fan or blower 13 will be drawn by suction from either or both of the sample boxes.

The sample boxes 11 and 23 may be opened to the atmosphere at their ends opposite the connections to the pipes 12 and 24, in which case the air will be drawn through the sample boxes entirely by suction from the fan or blower 13, but preferably such opposite ends of the sample boxes are connected by pipes 26 and 27 to a Y-shaped connector 28 which is in turn connected to the outlet side of a fan or blower 29, so that the two sample boxes will be supplied with a source of compressed air. In some instances where the fan or blower 29 is utilized, it may be possible or desirable to omit the suction fan or blower 13 and directly connect the pipes 12 and 14. The forcing of the air through the sample boxes by the pressure of the blower instead of dependingupon more or less uncertain suction is advisable in many cases, owing to the fact that any leakage in the sample boxes by reason of poor contact of the webs with the open faces of the boxes will not materially affect the indications to be olnained from the air which passes through the boxes to the hygrometric instruments. Where the air is drawn through the boxes by suction, any air entering the box by suction may pass direct- 1y into the pipe 12 or 24 through the points of leakage without having remained in contact with the web for the expected duration, and therefore an uncertain and incorrect humidity indication or control would result. It will be understood. however, that it is perfectly feasible to utilize both the fan and blower if desired, or either one alone may be employed.

I also prefer to provide means for shutting off one of the sample boxes automatically in case it is found desirable, such as for example the sample box connected to the paper Web when that web breaks. Any suitable means for shutting off such branch connections through the sample box 23 may be employed, but I found that a vane 30 disposed in the Y-connector and pivoted therein at the apex or intersection of the two arms may be employed satisfactorily. Such a vane may be shifted about its pivotal support at the intersection of the two arms, so as to cut ofi either branch 26 or 27, or it may remain in a neutral or intermediate position in which it permits passage of air through both branches in approximately equal or desired proportional amounts. This vane is preferably biased to this intermediate position in any suitable manner, such as by a counter weight 31 connected thereto. A second and shorter vane 32 may be connected to the vane 30 and disposed to extend laterally therefrom at its pivot, and in a direction across the branch 27 when the main vane 30 is in its intermediate position as shown in Fig. 5.

In the event that the paper web breaks, the sample box 23 will be opened along its face, and therefore, there will be an increased rush of air through the branch 27 into the sample box 23, from which it escapes into the air instead of passing through the hygro-- metric instrument. The vane 32 is of such relative size that this increased velocity of the air in the branch 27 will swing the main vane 30 in a direction to cut off the supply of air to the branch 27, the air or static pressure in the connector caused by the blower 29 serving to hold the main vane 30 in the position where it closes the branch 27.

During the normal operation of the device, the air or gas flows through the sample boxes and the branch connections rather slowly. and the vane 32 will not be materially affected bv this relatively slow moving gas or air. With the shutting off of the branch to the sample box 23, automatically, the drier rolls will receive their steam supply subject to the control of the sample box 11 which is influenced by the drier felt, and as the latter becomes drier owing to its lack of contact with the moist paper web, the steam or heat supply will be out off and held off during a continuance of this condition in the machine, so that overheating of the drier rolls will be prevented. If the paper web is broken only for a short interval, the drier felt will not be dried out sufliciently to cause a complete cutting off of the steam or drying medium, and consequently as soon as the web is again startedthe operation will continue as before.

In the event of breakage of the paper web as hereinbefore mentioned, there might be a tendency for some of the gas in the pipe 12 to pass out through the sample box 23, instead of passing through the hygrometric instrument 15 as intended, but with the use of the suction fan 13, this air will largely be drawn through the intended path to the in-l strument 15. Furthermore, with the air in the pipe 12 under pressure for supplying the needs of the suction fan 13 there will be little or no tendency for air to enter the pipe 24 through the open sample box 23 where the paper web is broken. Otherwise, the breaking of the paper web would allow passage of the air to the hygrometricinstrument through the open sample box 23, instead of passing through the other sample box 11 in contact with the drier felt as desired.

It will be observed that during the normal operation of the machine, the hygrometric instrument and control of the temperature of the drier rolls will be influenced directly from either the drier felt or paper web, or both, and that if the paper web breaks the sample box cooperating with the paper web is automatically rendered ineffective, in so far as its influence upon the temperature control of the drier rolls is concerned. Overheating of the drier rolls is prevented in the event that the paper web is not again promptly started through the machine.

It will be understood that various changes in the details, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention, as expressed in the appended claims.

I claim as my invention:

1. In a method of determining the moisture condition of a web of paper or the like moving into and out of contact with a drier felt, which consists in directing a current of gas into intimate contact with a portion of the said drier felt near where the latter and the web get out of contact with each other and subsequently determining the moisture condition of the gas.

2. The method of determining the moisture content of a moving web of material passing over driers and in contact with a drier felt, comprising confining and directing a current of gas in intimate contact with a portion of said drier felt so that said gas partakes of the moisture condition of said felt, and subsequently measuring the moisture content of said gas as an indication of the moisture content of said felt and web of material.

GEORGE S. WITHAM, JR. 

